In the field of photomechanical processes using silver halide photographic materials, there is a demand for photographic light-sensitive materials having satisfactory image reproducibility of originals, stability of processing solutions, and simplification of the replenishment system, in order to cope with the recent diversity and complexity of printed materials.
In particular, originals in line work are comprised of photo-composed letters, hand-written letters, illustrations, and dot prints, and thus contain images having different densities or line widths. There has therefore been a demand for a process camera, photographic light-sensitive material or image formation system which enables one to reproduce the original with good reproducibility. In the photomechanical processing of catalogues or large posters, on the other hand, enlargement (spread) or reduction (choke) of a dot print is often required. When a dot print is enlarged in plate making, the line number becomes small and the dots are blurred. When a dot print is reduced, the line number/inch ratio becomes larger and the dots become finer than in the original. Accordingly, an image formation system having a broader latitude is needed to maintain reproducibility of dot gradation.
A halogen lamp or a xenon lamp is employed as a light source of a process camera. In order to obtain photographic sensitivity to these light sources, photographic materials are usually subjected to orthochromatic sensitization. However, orthochromatic photographic materials are more susceptible to the influences of chromatic aberration of the lens and thus susceptible to image quality deterioration. The deterioration is conspicuous when a xenon lamp is used as a light source.
Known systems meeting the demand for a broad latitude include a method in which a lith type silver halide light-sensitive material containing silver chlorobromide (containing at least 50% of silver chloride) is processed with a hydroquinone developing solution having an extremely low effective sulfite ion concentration (usually 0.1 mol/l or less) to thereby obtain a line or dot image having high contrast and high blackening density in which image areas and non-image areas are clearly distinguished. According to this method, however, development is extremely unstable against air oxidation due to the low sulfite concentration of the developing solution. Hence, various efforts and devices are required to stabilize developing activity, and the processing speed is quite slow, reducing working efficiency.
There has thus been a demand for an image formation system which eliminates the image formation instability associated with the above-described lith development system and provides a superhigh contrast image by using a processing solution having a satisfactory preservation stability. In this connection, it has been proposed to process a surface latent image type silver halide photographic material containing a specific acylhydrazine compound with a developing solution having a pH between 11.0 and 12.3 and containing at least 0.15 mol/l of a sulfite preservative (thereby exhibiting satisfactory preservation stability) to form a superhigh contrast negative image having a gamma exceeding 10, as disclosed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606, and 4,311,781. In this new image formation system, silver iodobromide and silver chloroiodobromide as well as silver chlorobromide may be used, whereas the conventional superhigh contrast image formation systems are applicable only to photographic materials comprising silver chlorobromide having a high silver chloride content.
While the above-described image formation system exhibits excellent values in dot quality, stability of processing, rapidness of processing, and reproducibility of originals, a system which provides further improved reproducibility of originals is needed to cope with the recent diversity of printed materials.
In an attempt to improve image quality, a method using a redox compound having a carbonyl group which is capable of imagewise releasing a development inhibitor is known as disclosed, for example, in JP-A-61-213847 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, extension of dot gradation is insufficient, even with these compounds.
There is therefore a need for a light-sensitive material which forms a high contrast dot image using a stable developing solution and whose tone is controllable over a wide range.
On the other hand, improvement in working efficiency in page make-up and dot-to-dot work (a so-called contact work) has been attempted by performing the work in a brighter environment. Accordingly, light-sensitive materials for plate making which can be handled in a bright room environment and exposure printers for these materials have been developed.
The term "light-sensitive material for a bright room" as used herein means a light-sensitive material which can be safely handled for a long time with a safe light which includes no ultraviolet light component and has a wavelength of substantially 400 nm or more.
A light-sensitive material for a bright room which can be used in page make-up and in contact work, may be exposed to light while in intimate contact with a developed film having a letter or dot image (i.e., original) to effect negative-positive or positive-positive conversion. The light-sensitive material should (A) have the ability to perform negative-positive conversion of a dot image or a line or letter image according to the dot area or the line or letter image width of the original, and (B) have an ability to control the tone of the dot image or the width of the letter or line image. Light-sensitive materials for bright room contact work which meet these requirements have been provided.
However, when a conventional light-sensitive material for a bright room is used in bright room contact work in the highly technical image conversion operation called superimposed letter image formation by contact work, the resulting superimposed letter image is poor in quality as compared to that obtained by the technique involving dark room contact work using a conventional light-sensitive material for dark room contact work.
The method of superimposed letter image formation by contact work is illustrated in detail by reference to FIG. 1 of JP-A-2-293736. A film (2) having a letter or line image shown in black (i.e., the line original) and a film (4) having a dot image shown in black (i.e., the dot original) are adhered to transparent or translucent bases (1) and (3), respectively. Bases (1) and (3) are usually polyethylene terephthalate films having a thickness of about 100 .mu.m. The line original and the dot original are superposed on each other to make an original. The emulsion layer of a light-sensitive material (5) for contact work is brought into contact with the dot original (4) and then exposed to light. The exposed light-sensitive material is then subjected to development processing to form a white line image within a dot image.
It is important in the above-described superimposed letter image formation that the negative-positive conversion be conducted precisely according to the dot area of the dot original and the line width of the line original. As is apparent from the Figure, the dot original (4) is in intimate contact with the emulsion layer of the light-sensitive material (5). On the other hand, line original (2) is not directly superposed on light-sensitive material (5). Rather the base (3) and dot original (4) are interposed therebetween. Therefore, when the light-sensitive material (5) is exposed to light at an exposure amount sufficient to effect negative-positive conversion faithfully to the dot original, the exposure through the line original is through base (3) and dot original (4), causing a reduction of the line width of the transparent line image. This causes deterioration of the superimposed letter image quality.
In order to solve the above problem, systems using a hydrazine derivative have been proposed as disclosed in JP-A-62-80640, JP-A-62-235938, JP-A-62-235939, JP-A-63-104046, JP-A-63-103235, JP-A-63-296031, JP-A-63-314541 and JP-A-64-13545, but sufficient effects have not yet been obtained, leaving a need for further improvements.
Additionally, systems using redox compounds which release a development inhibitor upon oxidation together with the hydrazine derivative are disclosed, for example, in JP-A-61-213847, JP-A-64-72140, JP-A-2-285340, JP-A-3-87733, JP-A-293736, JP-A-2-308239 and JP-A-3-110544.
As described above, by using a nucleating agent and a redox compound capable of releasing a development inhibitor upon oxidation, dot image reproducibility in terms of spread and choke is improved. The image quality of fine line or a transparent part of fine line is improved with respect to light-sensitive materials for photographing. Moreover, the improvement in image quality with respect to the requirements (A) and (B) described above is achieved for light-sensitive materials for contact work.
However, with light-sensitive materials containing a nucleating agent, there is the disadvantage that black peppers are formed, particularly when a developing solution which is fatigued upon oxidation by air is employed. Thus, one cannot take advantage of the features of the light-sensitive materials. Therefore, various methods for reducing the occurrence of black peppers have been investigated. For instance, a method wherein a trihydroxybenzene derivative is incorporated into a light-sensitive material is described in JP-A-2-310555, and a method wherein a hydroquinone derivative is incorporated into a light-sensitive material is described in Japanese Patent Application No. 2-127480. However, these methods have the disadvantage that the effect for restraining black peppers is decreased or that the occurrence of black peppers is rather promoted during the preservation of light-sensitive materials containing these compounds. Thus these methods are not yet satisfactory, and further improvement is needed.